Envelope Renovation Research Articles

Multi-objective optimization of rural residential envelopes in cold regions of China based on performance and economic efficiency

Building envelope renovation solutions are critical to building performance and post-renovation economics. Building renovation is easier to carry out if the impacts of building envelope renovation solutions on building performance and post-renovation economic efficiency can be foreseen and a more sustainable and efficient renovation design can be achieved. This paper explores the optimal design of building envelope renovation using genetic optimization algorithms and statistical analysis methods, taking the performance of the renovated building and the economic efficiency of the renovation solution as the starting points. In Qingdao, a cold region of China, a survey was carried out on typical rural areas in seven regions. The selected design variables include the external wall and roof insulation material type(TWall, TRoof), external wall and roof insulation thickness(δWall, δRoof), type of window construction(TWc), and area radio of the window to the wall(WWR). Minimization of total building energy consumption(E) and renovation cost(COSTRE) and after renovation maximization of the combined incremental cost-benefit ratio over a 20-year life cycle(CICBR20-year life-cycle), effective natural daylighting illuminance(UDI), and percentage of time spent in indoor comfort(PTC) were considered in the optimization of the envelope. The results show that in cold regions, different envelope renovation solutions affect the optimization objectives to different degrees; changing the south-facing window-to-wall ratio(S_WWR) has a bigger effect on E, PTC, and UDI; and choosing different TRoof has a bigger effect on COSTRE and CICBR20-year life-cycle. Renovation of the selected typical rural residence with the optimal solution results in an energy-saving rate(Re) of 53.08 %, an increase of 940.86 h/year in annual indoor comfort hours(HIC) and 377.00 h/year in annual effective natural lighting hours(HUDI).

Energy Efficiency Analysis of Building Envelope Renovation and Photovoltaic System in a High-Rise Hotel Building in Indonesia

The development of high-rise buildings worldwide has given rise to significant concerns regarding their excessive electricity consumption. Among the various categories of high-rise structures, hotels used for business and conferences stand out as particularly extravagant in their energy use. The consequence arising from excessive energy usage is an escalation in carbon emissions, which is a primary driver of global warming. Therefore, this study aims to investigate the energy use intensity (EUI) of a hotel building located in Jakarta, Indonesia. In order to improve energy performance, this study explored various options for renovating the building envelope, such as incorporating insulation and a roof covering, as well as implementing building-integrated photovoltaics (BIPV). The building envelope renovations demonstrated a notable reduction in energy use by 15.8–27.7% per year. BIPV, such as curtain walls and double-skin façades, generated an energy use reduction of 4.8–8.6% per year. Remarkably, by combining the two approaches (i.e., adding insulation and a roof covering in the building envelope and adopting BIPV as double-skin façades), the potential reduction in energy use reached up to 32.2% per year. The findings can assist decision-makers in developing building renovation strategies for high-rise buildings while considering energy conservation.

An Energy Self-Sufficient Alpine Hut: The Refurbishment of an Ex-Tobacco Farm Using Building Integrated Photovoltaics

The abandonment and deterioration of historic rural buildings in Europe raise significant issues, including hydrogeological risks, the loss of productive land, and cultural heritage decline. Despite being underestimated, these structures hold significant potential for cultural and productive activities. Renovating these structures is crucial for local communities committed to preserving their heritage, and it is a more sustainable approach than constructing new buildings. This study explores activities undertaken in the Interreg IT/AT project “SHELTER” in Valbrenta (IT): through a participatory approach involving communities, stakeholders, designers, and researchers, an energy concept is developed for refurbishing an abandoned tobacco farm, chosen by the community, to be an alpine hut. Due to the inability to connect to the city electricity grid, the new energy concept focuses on minimizing consumption through envelope refurbishment, efficient heating, and domestic hot water systems. Additionally, the integration of renewable energy sources, particularly Building Integrated Photovoltaics (BIPV), is emphasized to preserve the building’s original appearance. This study demonstrates the feasibility of meeting seasonal energy needs entirely through renewables and explores the potential integration of biomass for meeting annual energy requirements.

Improving energy efficiency in Portuguese buildings: Retrofitting façades with high reflectance finishing coat

The European Union must enhance energy efficiency in its building stock, given that buildings account for up to 40% of the EU's energy consumption. Currently, more than 85% of buildings have been in use for over two decades, with at least 75% lacking energy efficiency. Only 10% of the building stock achieves ‘A’ or ‘B’ ratings in energy performance certificates. To meet energy efficiency standards, retrofitting exterior walls with passive techniques, such as enhancing optical properties, proves highly effective. Employing high reflectance surfaces reduces solar heat absorption, thereby lowering cooling energy use. This study examines the impact of reducing surface temperature through an external thermal insulation system with a high reflectance finishing coat during building envelope renovation in various climatic zones in Portugal. Preliminary findings indicate that high reflectance has a more substantial effect on annual heat gain for moderately insulated walls than well-insulated ones. The effect varies with maximum air temperature, especially in hot summers. A change in reflectance can improve heat gain reduction, especially considering the cost of retrofitting with insulation materials. An optimal balance between reflectance and thermal resistance is key to achieving lower surface temperatures and reducing cooling energy demands for Portuguese climates.

Benefits assessment of cool skin and ventilated cavity skin: Saving energy and mitigating heat and grid stress

This study assessed the energy-saving and climate-adaptive potential of cool skin and ventilated cavity skin facade technologies in Seoul's high-rise apartment buildings. We created weather scenarios for historical, mid-term future, and long-term future conditions using Coordinated Regional Downscaling EXperiment (CORDEX) method. Building energy simulations were conducted on a South Korean high-rise apartment model to evaluate their performance under different weather conditions. The results indicate that cool skin and ventilated cavity skin technologies can save cooling energy during summers but lead to heating energy penalties in winters. Ventilated cavity skin outperforms cool skin, offering better cooling energy savings and reduced heating penalties. Combining both technologies yields the highest overall energy savings, with 7 %, 9 %, and 10 % cooling energy savings for cool skin, ventilated cavity skin, and the combined package, respectively. However, cool skin increases heating energy consumption by 5 %, while ventilated cavity skin has minimal impact on heating energy. These envelope technologies also reduce peak electricity demand by at least 5 %, 8 %, and 9 %, respectively. They contribute to heat stress reduction, enhance resilience, and decrease extreme heat risks for occupants during power outages by at least 18 % under various weather conditions. Considering the prevalence of aging high-rise apartments in South Korea, adopting these envelope renovation strategies can effectively reduce cooling loads, enhance thermal comfort, and boost resilience under future climates, while avoiding costly reconstruction.

A study of thermal performance enhancement of building envelopes by using corncob as construction material

The energy-saving design of buildings effectively reduces heating energy consumption, improves indoor environmental problems in traditional houses, and plays an essential role in alleviating the increasingly severe environmental and energy problems. This study reviews the status of research on building energy-saving renovation and environmental improvement in various countries and summarizes their relevant research experiences. It described the theories and methods of survey, experiment, and numerical simulation to provide a theoretical basis for energy-saving renovation and environmental improvement of residential houses. Furthermore, it introduces corncob concrete material to provide new materials for the renovation of an old building. This research is based on the coastal Liyuan houses in Qingdao, and the problems of Liyuan houses are identified through in-field investigation. Then, through experimental simulations, the application and efficiency of corncob materials in the thermal performance improvement of the envelope are explored. The renovation of old residential houses in terms of energy-saving and environmental improvement is proposed from envelope renovation.

Carbon Life Cycle Assessment and Costing of Building Integrated Photovoltaic Systems for Deep Low-Carbon Renovation

Building integrated photovoltaic (BIPV) systems can achieve high yields through high percentages of building envelope surface coverage associated with material savings by substituting conventional building envelope components and avoiding land-use change to install open-land PV installations. This article discusses the life cycle assessment (LCA) and the life cycle costing (LCC) of BIPV systems in timber-hybrid building extensions and envelope renovation systems of three exemplary buildings in the Republic of Korea: apartment, mixed-use commercial/industrial, and low-rise multi-unit residential. The BIPV system’s electricity production was quantified with simulation tools. Minimum and average carbon LCAs were calculated using a global product inventory database for 50 years. Greenhouse gas (GHG) emission savings by substituting conventional energy supplies were calculated based on the associated primary energy demands. LCC calculations were based on international datasets for BIPV LCC for 25 and 50 years. As a result, the BIPV system-associated GHG emissions can be decreased by up to 30% with a payback time of 12 (apartment) to 41 (mixed-use building) years for buildings with full PV coverage. The positive cumulative net present value (NPV) for both LCC scenarios encourages economic investments in building renovations with BIPV systems.

Development of a Plug-In to Support Sustainability Assessment in the Decision-Making of a Building Envelope Refurbishment

Existing studies provide evidence that buildings and the construction sector are the largest consumers of natural resources and carry the greatest responsibility for greenhouse gas emissions. In order to reverse this situation, future challenges involve utilising the lowest amount of resources possible. To this end, building refurbishment has become a crucial strategy, given its potential to improve operational energy efficiency and to extend the life span of existing building stock, thereby reducing the environmental impact while also providing social and economic benefits to our cities. Life cycle sustainability assessment (LCSA) has become one of the scientific community’s most widely recognised methodologies for the evaluation of the social, economic, and environmental dimensions (triple bottom line), as it assesses sustainability using quantitative metrics. However, the implementation of this methodology to support the refurbishment process at the project stage in building design tools, such as BIM, remains scarce. One of the main obstacles lies in the difficulties of accessing building information, given that the system boundaries only cover new materials and products. Hence, this study proposes a BIM plug-in developed to support multi-dimensional building material selection in the early design steps based on the LCSA of a building during the refurbishment stage and validates its application in a case study. The results show the viability of using this tool during the early design stages and demonstrate the consistency of the results for evaluating various material and product alternatives for the refurbishment of the envelope system of a multi-family residential building. This study contributes towards the integration of decision-making by providing real-time assessment of a building envelope.

Cost-Optimal Renovation Solutions for Detached Rural Houses in Severe Cold Regions of China

High heating expenses are observed in numerous Chinese rural houses located in severe cold regions due to the high heating demand, inferior envelope performance and low-efficiency heating equipment. The local traditional heating methods include Chinese Kangs and coal boilers with water-based radiators. The intermittent operation and manual regulation of these systems result in significant temperature differences and inadequate thermal comfort. This study presents the cost-optimal envelope renovation solutions with the minimized lifecycle cost (LCC) during a 20-year discount period and CO2 emissions of annual delivered energy consumptions. A single-family detached rural house in Harbin was used as a case building, illustrating the typical state of comparable houses in this climate context. Simulation-based multi-optimization analysis was conducted in this study using the building simulation tool IDA ICE and its integrated optimization tool AutoMOO. The results indicate that the cost-optimal renovation solutions with intermittent and continuous heating can cut CO2 emissions by 30% and 40%, respectively. The LCC with intermittent heating is still 7% greater than its pre-renovation case, which may require external financial support to encourage the renovation conduction, while the LCC with continuous heating decreased by 8% after renovation. According to the comparison results, cost-optimal solutions have significant advantages in both reductions of LCC and CO2 emissions over standard-based solutions. Moreover, utilizing intermittent heating is more effective than continuous heating in demonstrating the positive impacts of envelope renovation on increasing average temperature, decreasing temperature differences and lowering occupied time at low thermal comfort levels.

The impact of retrofitted ventilation approaches on long-range airborne infection risk for lecture room environments: design stage methodology and application

There is a continued need to improve the energy (and by extension carbon) performance of the existing building stock in Europe and globally. Recent experiences with the COVID-19 pandemic have demanded even more of the built environment disciplines when it comes to air quality and ventilation rates particularly in teaching environments which are seen as necessary developmental sectors for the learning of the population. As such it is important that these spaces are safe for students and staff where, until now, infectious disease risk assessments were not typical. In addition to this, there is a risk that envelope refurbishment (which is critical for energy performance) without the provision of adequate ventilation may lead to high-risk scenarios for occupants in university spaces and additional measures may be required. This study presents a design stage risk assessment methodology and applies this to evaluate different retrofitted ventilation approaches combined with additional control measures for a lecture room environment. A real case study lecture room in Ireland was used to demonstrate the methodology for evaluating the airborne infectious disease risk (using the Wells-Riley model) under different ventilation approaches (natural and mechanical), infiltration rates (existing and upgraded), class sizes and times, mask efficiencies as well as the use of an air cleaner. The methodology that was adopted was shown to be flexible and capable of considering a wide range of different retrofit and user specific combinations. The results from the evaluation indicate a wide range in event specific reproductive numbers, however, the use of a well-designed natural or mechanical ventilation system was seen as significant in stabilising or suppressing virus transmission and reducing the likelihood of highly reproductive events. It was found that combinations of measures with ventilation were the most effective at suppressing reproductive numbers. It is recommended that during known pandemics (in the short-term) infectious control strategies should use filtration (through masks or air cleaners) and adequate ventilation. Long-term refurbishment strategies should consider the provision of hybrid ventilation systems which integrate key energy saving measures (such as heat recovery and demand-controlled ventilation), virus control (such as HEPA filtration) and low energy cooling solutions (such as passive cooling).

Experimental and Numerical Analysis of Temperature Reduction Potentials in the Heating Supply of an Unrenovated University Building

Lowering the temperatures in heating systems is the key to decarbonizing the heat supply in the building sector, because it is a door opener to greater integration of renewable heat, the use of excess heat and to improve compatibility for heat pumps. This often fails because heating systems, especially in unrenovated building stock, usually require high supply temperatures. Previous studies on temperature reduction in existing buildings are performed mainly numerically, whereas in this research the numeric calculations are validated by measurements. For this purpose, a demonstrator with two different ceiling heating systems is integrated in the listed architecture building of the Technical University of Darmstadt and the achievable temperature reduction is investigated. Based on this, parameter variations are conducted through a simulation model in order to test the feasibility of the concept for the entire building. The results show that even with an unrenovated building envelope, a significant temperature reduction to below 45 °C is possible without exceeding the normative limits of thermal comfort. With moderate building envelope renovation, the reduction is possible even to below 36 °C. The measures investigated can make the building compatible with renewable heat potentials without negative impacts on the cultural heritage.

Integration of Energy Simulations and Life Cycle Assessment in Building Refurbishment: An Affordability Comparison of Thermal Insulation Materials through a New Sustainability Index

Energy efficiency and greenhouse gas reduction have become two of the most important issues to address in fighting climate change. Focused strategies have been implemented aiming at reducing the energy consumption of buildings since it is one of the most energy-intensive sectors, but they are mainly concerned with energy reduction without considering their environmental impact. The present work therefore aims at assessing the energy and environmental impacts of the use of insulation materials for building envelope refurbishment as the thermal coating. Reference buildings were used to perform energy simulations in representative cities of Italy and energy and environmental impacts of the most common and sustainable insulation materials were thus evaluated. Relevant outcomes have been focused on defining a new Economic and Environmental Sustainability Index (EESI) capable of considering both economic and environmental aspects; particularly, sustainable materials (such as cellulose fiber) can have the same affordability as traditional ones (such as polystyrene foam slab, glass wool, or stone wool) if environmental impact is also taken into account, despite their higher cost. However, according to EESI, the affordability of traditional insulation materials remains evident in the warmest climatic zones because of the lower energy needs of buildings.

What are typical levels of housing renovation? A typology based on Swedish public strategies

The gap between energy policy and potential energy savings through renovation, and what is carried out in practice has been in focus of previous research. Various influencing factors such as economy, organisation, and social relations versus tenants has been studied to design guidelines to bridge this gap. There is a lack of empirical studies of how renovation is planned, and what factors will influence the renovation measures that are implemented. This paper takes the starting point in 42 on-going and planned housing renovation projects 2018 – 2021 carried out by three municipal housing companies in one major Swedish metropolitan area. Based on the character of these, three main types of housing renovation are defined. The most current type of renovation is bathroom and piping while climate envelope renovation and deep renovation are less common. Energy saving is decoupled from renovation activities which will have implications for implementation of policy for energy efficient renovation.

Integrated building envelope performance evaluation method towards nearly zero energy buildings based on operation data

The thermal transmittance plays a decisive role in building energy efficiency design, which determined by standard in-situ measurement are obviously not equivalent to the practical building load level. There is still a lack of post-evaluation method that can separately evaluate the energy saving effect provided by integrated building envelope, especially for the nearly-zero energy building (NZEB) whose thermal inertia cannot be neglected. This paper proposed a model-based integrated building envelope performance evaluation method, which contains a reverse parameters identification and a forward load calculation. The data-driven lumped-parameter model represented by resistance–capacitance network (RC-model) reflects the integrated envelope performance, and four different model structures were designed for different treatment of thermal mass were compared. The applicability of the selected 7R6C model in the simulation of NZEB is demonstrated by the accuracy verification, sensitivity analysis of initial values of temperature node and uncertainty assessment of internal heat gain. A renovation case achieved an annual heating demand assessment result of 14.0 kWh/(m2·a) under typical annual meteorological data, which is lower than the limit value of a NZEB in cold region of 15.0 kWh/(m2·a). The evaluation results show that the envelope renovation meets the requirements of energy efficiency design. On the way to low-carbon buildings, the corresponding post-evaluation method needs to be gradually improved.

Carbon-neutral building renovation potential with passive house-certified components: Applications for an exemplary apartment building in the Republic of Korea

Building energy consumption for heating and cooling and the comparatively short building lifecycle help account for the increasing ratio of the building sector's greenhouse gas (GHG) emissions. To counteract this increase, sustainable building envelope renovations can minimize GHG emissions through the extension of building lifecycle, saving of construction material, increased energy efficiency, and reduced heating and cooling energy demands. To reduce the GHG emissions of energy efficient building envelope renovation systems, this article compares the Life Cycle Assessment (LCA) results of different Passive House (PH) certified building envelope components regarding their GHG emissions per area unit. Based on PH-certified components, different building envelope renovation components were developed. The LCA facilitated the identification of components with the lowest carbon emissions, which were applied in the PH-conforming renovation model of an exemplary apartment building in Seoul, Republic of Korea. The LCA results over a service life of 50 years illustrate that the highest GHG emissions are associated with the renovated building's primary service energy demand, followed by windows, and the transport of materials. These research findings facilitate the environmental impact determination of multiple PH-standard building renovation systems, and support the planning of building renovations with minimized carbon footprints and service energy demands.

Hybrid timber-based systems for low-carbon, deep renovation of aged buildings: Three exemplary buildings in the Republic of Korea

The ageing of buildings is associated with their degradation. By the end of a building's operative life, two solutions are provided: demolition and new construction, or renovation. New construction can cause higher greenhouse gas equivalent emissions than renovations, related to higher demand for building materials, processes, and waste management. Conversely, building renovation requires greater effort in planning and implementation. Moreover, when improperly planned, renovation might ensure only limited improvements in building performance. This study presents three renovation systems based on hybrid timber technologies for three common case-study building types in the Republic of Korea: apartment, low-rise residential, and mixed-use (industrial–commercial). Following analysis of the current regulations for building component performance in Korea, three modular building envelope renovation systems have been developed: (i) cross-laminated timber, (ii) glue-laminated frame with integrated timber stud panels, and (iii) steel frame with integrated timber stud walls. The development of the three systems focuses on designing modular self-supporting components that allow both horizontal and vertical extension, and the structural support of occupied buildings. The hybrid timber-based construction provides a low-carbon alternative to demolition and new construction, helping to solve spatial constraints to renovation determined by the high urban density of Korean cities.

A Forecasting Method for Macro-Control Policy of Heating Energy Consumption and Carbon Emissions Based on Building Area and Energy Intensity: A Case Study of Northern China

In response to extreme climate change, China has set a goal of reaching emission peak by 2030 and achieving carbon neutrality by 2050. Energy conservation and emission reduction of building heating in northern China are key to achieving this goal. Based on building area prediction and energy consumption intensity, this paper establishes a model for calculating heating energy consumption and carbon emissions in northern residential buildings at the macro level, which provides a basis for formulating policies related to heating and emission reduction in northern buildings. Based on the research method of scenario projection, combining the carbon emission subsets and future heating energy mix projections in northern China, the heating energy consumption in northern China decreases to 175, 149 and 135 Mtce in 2050 under the baseline, medium control and strict control scenarios, respectively. The heating energy consumption in the northern region should be controlled at least under the medium control scheme. Under this scenario, building heating carbon emissions in the north could be reduced to 450 MtCO2 by 2050, or 280 MtCO2 if more stringent abatement technologies are adopted. In order to achieve this goal, a combination of energy-saving technologies must be used. The use of biomass and solar technologies should be emphasized in rural heating, while envelope renovation makes the greatest contribution to heating energy savings, with envelope renovation contributing up to 92 Mtce to urban heating.

A Case Study on a Stochastic-Based Optimisation Approach towards the Integration of Photovoltaic Panels in Multi-Residential Social Housing

The socioeconomic reality and the energy retrofit potential of the social housing neighbourhoods in Portugal are stimulating challenges to be addressed by research to pursue suitable energy efficient strategies to be integrated into these buildings. Therefore, this study explored a stochastic-based optimisation approach towards the integration of photovoltaic (PV) panels, considering different scenarios that combine the occupancy rate, the internal gains, the envelope refurbishment and the heating system efficiency. The optimisation approach has as its objective the minimisation of the life cycle cost of the photovoltaic system while using a limited space area on the rooftop for its installation. This study allowed concluding that the use of passive measures such as improving the thermal performance of the building envelope is essential to attain a lower optimal-sizing of a photovoltaic installation. The results reveal a decreasing trend in the PV optimal sizing, attaining a reduction up to 30% of the total number of PV panels installed on the sloped rooftop in several scenarios with 50% of occupancy rate. However, the impact can be greater when passive measures are coupled to more efficient heating systems, with higher COP, which result in a decrease up to 64% of the number of PV panels. Thus, the approach proposed is of paramount importance to aid in the decision-making process of design and sizing of photovoltaic installation, highlighting the practical application potential for social housing and a contribution for mitigation of the energy poverty of low-income families that live in these buildings.

Adaptation Strategies of Residential Buildings Based on a Health Risk Evaluation—A Case Study of Townhouses in Taiwan

Global warming increases the probability of extreme events and heat waves triggering severe impacts on human health, especially the elderly. Taiwan is an aged society, so residential buildings, which cannot withstand extreme temperature events, increase the risk of harm for the elderly. Furthermore, Taiwanese prefer to open the windows to reduce indoor high temperatures, which causes high levels of outdoor PM2.5 to flow indoors, leading to health risks. Therefore, this research proposes a strategy to create a house with a low temperature and a low PM2.5 health risk for the elderly based on building envelope renovation and windows user behavior patterns. The risk day is demonstrated as an index to evaluate the indoor environment quality, which is based on the number of days that exceed the health risk threshold. The results show that the performance improvement of the building envelope and control of the window opening timing can effectively reduce the risk days by 48.5%. This means that passive strategies cannot fully control health risks, and the use of equipment is necessary. Finally, if the current situation is maintained without any adjustment or strategy improvement, an additional 41.3% energy consumption must be paid every year to control health risks.

Plug and Play Modular Façade Construction System for Renovation for Residential Buildings

The present paper focuses on the architectural and constructional features required to ensure that building envelope renovation are safe, functional, and adaptable to the building stock, with particular focus on “plug and play” modular facade construction systems. It presents the design of one such system and how it addresses these issues. The outcome of early-stage functional test with a full-scale mock-up system, as well as its applicability to a real construction project is presented. It is found crucial to obtain high quality information about the status of the existing façade with the use of modern technologies such as topographic surveys or 3D scans and point cloud. Detailed design processes are required to ensure the compatibility of manufacture and installation tolerances, along with anchor systems that deliver flexibility for adjustment, and construction processes adapting standard installation methods to the architectural particularities of each case that may hinder its use or require some modification in each situation. This prefabricated plug and play modular system has been tested by reproducing the holistic methodology and new technologies in the market by means of real demonstrators. When compared to more conventional construction methods, this system achieves savings in a real case of 50% (time), 30% (materials) and 25% (waste), thus achieving significant economic savings.